It works ! Though there are still some problems.
For example : In the qml components ( embedded in QQuickWidget)
I have a button, when I hover on that button and move the mouse outsite the QQuickWidget "button.hovered" is still true . It's not correct ! Hope it will be fixed in the stable version.

Qt 5.4 is in final stages of development, so if this bug is not reported already, there is little change it will get fixed. But you can check on Qt bugtracker. This is definitely a bug and should be fixed.